1. Field of the Invention
The present invention relates to a protective film for a polarizing plate, and further to a polarizing plate and a liquid crystal display device each using such a protective film.
2. Description of Related Art
Triacetyl cellulose (TAC) has favorably been used for protective films for a polarizing plate. A polarizing plate generally has a polarizer between two protective films. Since TAC is pervious to moisture to a degree, when polarizing plates using TAC films are exposed to the atmosphere with high or low humidity for the long term, the TAC films become a cause of light leakage in a display having the polarizing plate and the like and there are cases where retention of display quality becomes impossible, notably in the display of the TN mode.
Reduction in thickness of TCA film in answer to the recent need for reduction in thickness of polarizing plate has sometimes led to degradation in moisture permeability and lowering of dimensional stability. It is difficult for a TCA film having a thickness below 40 μm in particular to impart sufficient durability to a polarizing plate.